Staying Connected - September 2012

Cleaning and Sterilization of Medical Cables and Connectors

Unless designed for single use, medical cables and leads will almost certainly require cleaning, disinfection or sterilization.  Depending upon the intended use, cleaning may range from a simple wipe down with soap to the elimination of all micro-organisms by sterilization, or something in-between.

How cables and connectors are required to be cleaned, and equally important, how they are likely to be cleaned should be addressed early in the design process so that the most appropriate materials and production processes will be used.



Most medical cables only
contact unbroken skin and are
classified as non-critical for
cleaning and disinfection

Non-Critical Classification

Based on the risk of contamination spreading from a device to a patient, three levels of disinfection are defined based on a strategy developed by Dr. Earle Spaulding in the 1960’s.  Dr. Spaulding was the Chair of the Department of Microbiology and Immunology at Temple University School of Medicine between 1949 and 1972.

When considering disinfection or sterilization, both Spaulding and the EPA classify medical cables and leadwires as “non-critical”.  Medical cables and leads typically come in contact with unbroken skin and do not normally come in contact with mucous membranes.  Non-critical devices typically require only cleaning and low-level disinfection.  If cables or wires come in contact with broken skin or mucous membranes, a higher level disinfection is required.

Minimum Cleaning and Disinfection Standards

ANSI/AAMI EC53 established minimum standards for cleaning and disinfection of ECG Cables and Leadwires.  Section 4.3.1 of the standard details cleaning and disinfection requirements:  “The trunk cable and patient leadwires shall be capable of being cleaned and disinfected 15 times with the following materials per section 5.3.1:

  • green soap or alcohol-free hand soap
  • 2% glutaraldehyde solution (such as Cidex)
  • Sodium hypochlorite (bleach) solution 10% in water


Common glutaraldehyde
disinfectants are recommended
for cleaning most medical cables


Alcohol based solutions or other solvent based cleaners are not recommended for cleaning medical cables because they may dry out the jacket causing it to become brittle and fail prematurely.  However, engineered plastics such as Santoprene® offer good to excellent resistance to isopropyl alcohol or other alcohol based cleaners.

Additionally, ANSI/AAMI EC53 section 4.4 establishes sterilization exposure requirements.  If no sterilization method is specified by the cable manufacturer, the standard provides an ethylene oxide sterilization cycle that is repeated ten times.  After ten cycles, “all labeling and performance requirements of this standard shall be met after sterilization.”

Cable Jacket Material

The outer jacket is one of the material considerations when designing a medical cable assembly or leadwire.  The jacket material is not only the part of the cable or wire that is most visible; it plays a large role in the performance of the finished cable assembly.  A cable jacket offers mechanical, chemical and environmental protection to the conductors within the jacket.



Autoclave is the most common
sterilization method and is unsuitable for
cables made of PVC or polyurethane

Because the jacket is exposed, the conditions the cable will be used under and how it will be cleaned or disinfected should be considered early in the design stage.

The following table offers guidelines as to the suitability of common cable materials based on various cleaning, disinfection and sterilization methods.  These materials are commonly used for both cable jackets and molded assemblies.

Cleaning and Disinfection

Material

Sodium Hypochlorite (bleach 10%)

Isopropyl Alcohol

Glutaral-dehyde (Cidex)

PVC

Good

Good

Fair

TPE/TPR

Excellent

Excellent

Excellent

TPU

Poor

Poor

Good

Silicone

Good

Excellent

Good

Sterilization

Material

Autoclave

Gamma

Ethylene oxide (ETO)

VHP1 (Sterrad)

Paracetic Acid (Steris)

PVC

Poor

Excellent

Excellent

Good

Good

TPE/TPR

Fair/Good

Excellent

Excellent

Good

Good/ Excellent

TPU

Poor

Excellent

Excellent

Good

Good

Silicone

Excellent

Excellent

Good

Excellent

Good/ Excellent

1- Vaporized Hydrogen Peroxide

Common Cable Jacket and Overmold Materials

  • PVC is one of the lowest cost cable materials.  It is commonly used to insulate conductors and as cable jacket material as well as for molded components.  PVC offers good resistance to alcohols, most solvents and alkalis, but is not suitable for steam sterilization by autoclave.
  • TPE/TPR (Thermoplastic Elastomer or Thermoplastic Rubber) - These materials are often referred to by the trade name of Santoprene®.  TPE/TPR materials have excellent chemical resistance and are suitable for cleaning and disinfection by most methods.  If designed appropriately, TPE/TPE cable assemblies can withstand several hundred steam autoclave cycles.
  • TPU – Thermoplastic Polyurethane offers excellent mechanical properties including abrasion resistance and tear strength.  Disadvantages of polyurethane material include poor resistance to some common cleaning agents and high temperatures making them unsuitable for sterilization by autoclave.
  • Silicone – Silicone is both very flexible and offers very high flex life.  It is the most common choice where a high number of sterilization cycles by autoclave are required.  Silicone cables can also be disinfected with most common solutions.  However, silicone is less durable than most other materials used for wire and cable jackets.  It is easily cut and offers poor tear resistance.


Unless specifically designed to be
submerged – an IPX7 rating - soaking
cables or leadwires is not recommended
and can lead to premature failure


Cleaning and Disinfection Issues

When used at higher than the recommended dilutions, cleaning and disinfection agents can damage medical cables and leads.  An all too common error is that disinfection solutions such as glutaraldehyde or sodium hypochlorite (bleach) are used at much higher concentrations than intended, causing damage to medical devices such as cables and leads. 

Unless the cable assembly, including connectors, is specifically designed and manufactured to be submersible, having an IP rating of X7 or higher, it should not be cleaned or disinfected by submersion in a liquid.  And, unless designed to have an ingress protection rating of X3 or higher, cables and connectors should not be subject to being sprayed or saturated with liquid cleaning agents.  Even if the cleaning agent is compatible with the material used to manufacture the device, ingress into contacts or terminations may cause unseen corrosion, poor performance or failure.

Because they are commonly found in healthcare facilities, cables are often cleaned with wipes saturated with quaternary ammonium compounds containing didecyl dimethyl ammonium chloride.  While these wipes are very efficient for cleaning and disinfecting, they are specifically designed to be used on “hard, non-porous surfaces.”   With continued use these cleaning agents will degrade many plastics, including cable and wire jackets, leading to shortened service life.  Common trade names of wipes designed to disinfect hard surfaces are “CaviWipes” and “Sani-Cloth.”



Quaternary compounds, such as didecyl
dimethyl ammonium chloride, which are
designed to disinfect hard surfaces, are
not recommended for cleaning cables
and lead sets

Summary

How a medical cable assembly will be cleaned and disinfected should be considered at an early stage of product development so that the most appropriate materials are specified.  If you would like more information, or if you would like to take advantage of our experience in designing cable systems to withstand cleaning and sterilization, contact us at +1 949-477-9495 or via email to customercare2@affinitymedical.com.

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Meet Heather Hibben – Affinity Medical Quality Engineer


Heather Hibben -
Affinity Medical Quality Engineer


Heather Hibben joined the Affinity team in early June 2010 as Affinity’s first Quality Engineer.  Before joining Affinity, Heather worked six years for a company that specialized in aerospace and military defense components.  It was there that she found her love of quality and functioned both as the Sr. Quality Engineer and Lean Six Sigma Black Belt.

When asked what she likes most about her job, Heather replied, “I like the people most of all!  We’ve got such a unique dynamic here, and above all, we’ve got a happy & healthy culture. We easily come together to overcome any challenges we face.  While I am a career driven woman, I have been fortunate enough to establish a healthy balance between work and play; however, I am continuously on the lookout for learning new and challenging things.”   



Heather –right- with Affinity Quality
Manager, Cecille Vickers and Retired
Quality Manager Cindy Oldynski - center

Heather truly loves being in Quality and enjoys digging into issues.  When conducting investigations, she notes that the obvious cause is often not the root cause and she frequently uses her Six Sigma tools for improvement opportunities.  “Lean Six Sigma fascinates me, and having a career with new and exciting projects keeps me motivated!”

“Heather adds a lot of positive energy to the company,” said Hank Mancini, Affinity’s Business Development Manager.  “Besides being full of energy, Heather always has a smile and is willing to help with anything.  It is really a pleasure to work with her.”
Heather grew up in Huntington Beach in Southern California.  “I am a beach girl at heart,” said Heather.  “I went to school at University of Kansas and besides getting a good education; it made me realize how lucky I was to grow up at the beach.”

When asked to describe herself, Heather said “I’m a fun-loving, loyal, adventurous, quick-witted, and otherwise self-sufficient, joke-cracking gal!  I always love a good laugh!  I am so lucky to have such amazing friends and family members who I spend a lot of time with travelling, vacationing, and sampling great wines!  Generally, I just like to have a good time no matter what I’m doing.  I really like quirky & artsy things (specifically steampunk art), and I’m also a huge SyFy fan.  I enjoy watching cheesy “B” monster movies!  I’ve always led an active lifestyle; playing various sports, and even scuba diving - I love to swim with sharks, but hate to be near bugs!  Even though I don’t like spiders and other insects, I don’t like to kill them.  I love all animals and have 3 cats & a dog of my own.”

Heather also enjoys growing her own fresh vegetables in her backyard, cooking, working out, training her German Sheppard, and of course spoiling her new Godson every chance she gets!

“The environment at Affinity is so welcoming; and our guests often mention this to me.  The level of commitment and dedication to quality is so refreshing,” commented Heather.  “Our production team is awesome.  One hundred percent on-time delivery in June really shows that commitment.  I’m really happy to be a part of the Affinity family.”

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Modular Medical Connector System

Hybrid Electronic Enclosures


Clear clamshell case holds and protects
circuitry from direct overmolding


Finished assembly after overmolding
inner clamshell with softer
thermoplastic material

Hybrid enclosures are a combination of hard plastic cases overmolded with a softer thermoplastic material.  Typically for this type of construction, the clamshell case is filled with a light weight potting material before being overmolded.  If this is not done, mold pressures could collapse the case.

There are several advantages to this type of enclosure including:

  • Protecting the electronic components from the temperature and pressure of direct overmolding
  • Achieving a lighter weight assembly by using a fill material that is lighter in weight than mold material
  • Producing larger overmolded electronic packages than could be achieved by direct overmolding.

With a hybrid design, the outer mold can be designed to follow the contours of the inner case allowing a uniform wall thickness.  A uniform wall thickness will typically produce a more consistent outer surface even when large assemblies are encapsulated by overmolding.

Summary

Incorporating electronic circuits into external enclosures can offer medical device manufacturers additional alternatives.  The Affinity engineering team has experience designing and manufacturing a wide variety of enclosures and incorporating circuits, connectors and cable assemblies.

For more information on how Affinity can help you with “smart cables,” external enclosures, custom cable assemblies and connectors, contact us at customercare2@affinitymed.com or call us at +1 949-477-9495.

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Announcements, Information and Trivia

Visit Affinity at Medica November 14th through 17th in Dusseldorf Germany.  The Affinity team, Mary, Bob, Hank, Jim, Didier and Roberto (from MPS) will be at its usual location in Hall 9,
Stand C74

If you would like to schedule an appointment at Affinity’s stand or at your company’s stand, please email Jim Itkin at jitkin@affinitymedical.com.



The Sun photographed by
NASA's Solar Dynamics
Observatory – Public
Domain image courtesy of
Wikimedia Commons


The Sun sets over the
Atlantic Ocean in Panama

 

Sun Trivia

The sun is 93 million miles from earth and this distance is often referred to as one astronomical unit (AU).

The Sun is composed primarily of hydrogen (75%) and helium (24%).

It takes light approximately eight minutes to reach the Earth from the Sun.

The sun contains 99% of all the mass in our solar system.

A cosmic year is the amount of time it takes the Sun to revolve around the center of the Milky Way, about 225 million years.

Panama is the only place in the world where one can see the sun rise on the Pacific Ocean and set on the Atlantic.

The Sun shrinks five feet every hour as hydrogen is converted to helium in nuclear fusion.